DP Biology (first assessment 2025)

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Question 23M.2.SL.TZ2.b

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Date May 2023 Marks available [Maximum mark: 3] Reference code 23M.2.SL.TZ2.b
Level SL Paper 2 Time zone TZ2
Command term Explain Question number b Adapted from N/A
b.
[Maximum mark: 3]
23M.2.SL.TZ2.b

L. purpureus can have purple or white flowers. Two pure-breeding varieties were crossed: HA 4 with white flowers and GL 424 with purple flowers. All of the F1 plants had purple flowers. The F1 plants were self-pollinated to produce an F2 generation. There were 97 plants with purple flowers and 38 plants with white flowers in the F2 generation.

Using a Punnett grid, explain the results of this cross.

[3]

Markscheme
  1. male and female gamete genotypes/alleles shown as P and p (or others following convention with a suitable key) in a punnet grid;
  2. F2 genotypes shown as PP, Pp, pP and pp;
  3. F2 phenotypes indicated for each genotype on the Punnett grid / 3 purple to 1 white ratio indicated;

 

Accept other upper-case and lower-case letters for the alleles.

No punnet grid = 2 MAX.

Allow ECF if alleles incorrect.

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